# The Evolutionary Utility of the Opposable Thumb **URL:** \ **Category:** Factual Questions\ **Created:** [August 12, 2006, 5:16am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411 "2006-08-12T05:16:31Z")\ **Posts on this page:** 15\ **Page:** 2
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [August 18, 2006, 6:02pm UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/21 "2006-08-18T18:02:56Z")
> [@Alex\_Dubinsky](#): > > Australopithecines were smarter than chimps and could walk better than them. Chimps and other apes can walk too, but they’re also very smart. Other animals sometimes stand up in the wild, but very few are able to walk far before falling over (at least without lots of training). If you say humans train themselves for walking, then try watching the olympics and seeing what trained humans are really capable of (to compare effectively). It might be that Australopithicines were “smarter” than chimps, but we really don’t know. Their brains, however, were close to chimp-size, so it’s reasonable to assume that their intelligence level was chimplike as well. As for walking better, so what? Chimps didn’t evolve to walk bipedial, while hominids did. That tells us nothing about their brainpower. It’s quite likely that bipedalism did, as a byproduct, spur further brain development since it feed up the hands for many other uses, but that came long after the adaptation to upright walking occured. There is simply no reason to link bipedalism with intellgence. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [August 19, 2006, 5:09am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/22 "2006-08-19T05:09:08Z")
> [@Excalibur](#): > > > [@](#): > > > > Quote:Originally Posted by Alex\_Dubinsky > > Australopithecines were smarter than chimps and could walk better than them. Chimps and other apes can walk too, but they’re also very smart. Other animals sometimes stand up in the wild, but very few are able to walk far before falling over (at least without lots of training). If you say humans train themselves for walking, then try watching the olympics and seeing what trained humans are really capable of (to compare effectively). > > > > You can’t build a segway with a pocket calculator. You need brains for these things (bipedalism and movement precision). > > You’re so scattered that I can’t tell what you even think you’re saying. At any rate, the evolutionary line that led to humans developed true bipedalism long before it developed human-like brains. All bipedalism requires, anyway, is a bit more motor sophistication. I’m trying out a compact writing style. Too bad it’s an excuse for you to tell yourself denial is a river in Egypt. I very clearly say bipedalism began evolving in apes long ago, and further argue that its sophistication has mirrored the growth of intelligence. I don’t understand why you assume bipedalism to be so computationally easy. You have to not only keep track of where dozens (hundreds?) of joints and muscles are, but you have to compute with exquisite precision where they will be. You do this not just by considering their velocities, but their momenta, kinetic energies, and frictions. Most challenging of all, you have to incorporate visual information and the 3D map of surroundings that it generates. And you must do all this repeatedly, all the time, every couple of dozen milliseconds. Bipedalism holds a huge advantage to all animals in being able to demonstrate larger size to predators or to reach for higher-lying fruits. That is why so many animals are able to stand up, such as bears. They also often take a few steps. Are you telling me that they inevitably end up falling over because they just feel like it? Of course bears can be trained to walk quite well on flat surfaces. This is why I brought up the Olympics (and acrobatics, martial arts, etc). Excalibur, I know you don’t like me. But you have a habit of letting it cloud your rationality. Of course I’m not saying that because you disagree with me you are stubborn. But replies of “I don’t know what you’re saying and I’m refusing to try to understand it” only belie your intelligence. > [@](#): > > My chihuahua does pretty impressive little stints as a biped and she doesn’t even have the hips or neck for it. Still manages to balance on her back feet and walk around for several minutes when she thinks whatever I’m doing in the kitchen might lead to food for her. If it takes a big brain to manage bipedal locomotion even when you’ve got the skeletal architecture for it, I’d imagine it would take an even bigger one to carry it off when you don’t. > > Trust me — she’s cute and, for a chihuahua, rather sweet, but not really the sharpest spine on the cactus. Same as bears: flat surfaces and training. However, dogs in general are quite smart (which is why they can walk despite not really doing it in the wild). > [@Lemur866](#): > > > [@](#): > > > > Quote:Originally Posted by Alex\_Dubinsky > > For example, (and this is hypothetical) what happens if a species evolves to be intelligent enough to look at each other and have an idea of who is fit and who isn’t. At first, this may start out very simply as the animals which look healthy and well-featured attract more mates (although, even at that point, the process has gotten pretty sophisticated). However, with further advancement, the overall process may honestly resemble artificial selection more than natural. > > … > > To argue more effectively with an example, humans in times of little food are more likely to think plumpness to be attractive. While natural selection for even blind organisms would push towards the energy-stockpiling adaptation, the process has been improved and has gotten faster because of the evolution of our brains along with the instincts which make us think that way. > > This process is generally known as sexual selection. But it isn’t tied to increased brain power, rather some simple signal that potential mates respond to. So female peafowl dig peacocks with big fancy tails. They don’t have sophisticated brains that tell them that a peacock with a fancy tail is more likely to be fit/healthy than a peacock with a raggedy tail, they just dig bad boys with big tails. And so in a sexual arms race tail sizes increase to the spectacular sizes we see in peacocks today. Or it could be something else…a particular song, a patch of feathers, a mating dance, different species have different signals. > > [Sexual selection - Wikipedia](http://en.wikipedia.org/wiki/Sexual_selection) Right, sexual selection is often a game that simply goes around in circles. However, my example wasn’t with feather colorings but energy storage. Maybe my example shouldn’t be called sexual selection. More likely, we shouldn’t consider sexual selection to always go nowhere. So the question now is, should episodes of sexual selection which contribute to larger-scale evolution be also considered to be a fascet of natural selection? It is a discussion of semantics, however. The important point is to recognize that processes evolve which speed evolution. > [@John Mace](#): > > There is simply no reason to link bipedalism with intellgence. I’m sorry you didn’t receive your own reply. I have a habbit (for good or bad) to write as I read and by now I’ve written quite a bit. However, I said many things above which address your points and I hope you stay active in the discussion. > [@John Mace](#): > > It’s quite likely that bipedalism did, as a byproduct, spur further brain development since it feed up the hands for many other uses, but that came long after the adaptation to upright walking occured. Actually, that’s a very good point. I still believe opposable thumbs themselves evolved in the trees where bipedalism is N/A. However, opposable thumb precision, unlike what I had been leaning towards before, was probably more directly a biproduct of bipedalism and not of intelligence per se. However, intelligence is still required to allow for and make good use of precision, but that capability was already in place once the brain grew advanced enough to walk. This is a subtle point, and only people who have been following the discussion closely will care for it (there was a post a while back arguing that it is thumb precision, not merely opposable thumbs, which is important). ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 5:29am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/23 "2006-08-19T05:29:08Z")
> [@AHunter3](#): > > We of the **five digits** , in the form of 4 fingers and a convenient thumb that closed towards them in the opposite direction, were by virtue of that design said to be toolmakers and tool-deployers. Toss a couple hundred millennia of learn-and-extend on top of “hey check it out, stone scrapers” and you’ve got homo sap footprints on the moon and urban blight and reality television, yeah? no? I always understood the idea to be that opposable thumbs are part of what enabled us to use tools etc. -FrL ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 5:35am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/24 "2006-08-19T05:35:13Z")
> [@Darwin's Finch](#): > > Natural selection is not a “thing” upon which, well, _anything_ can act. Especially not “itself”. It is a shorthand for statistical probabilities; it is the sum total of all external forces, events, conditions and happenstances which affect the relative frequencies of gene alleles within a population. As such, there’s really no way for natural selection to feedback on itself (keeping in mind there is neither an “it” nor a “self” involved…) to make itself faster / more efficient / whatever. > > Remember that natural selection is simply an analogous process to artificial selection. Except, instead of humans selecting individuals based on traits which we desire, nature is “selecting” organisms based on traits which are most advantageous to themselves. Advantages and disadvantages are translated into likelihoods of success or failure in terms of passing one’s genes on to subsequent generations. Regardless _how_ populations evolve under the scrutiny of NS, NS will still operate in the same way. I would have thought that species could be naturally selected, under certain circumstances, for their being especially prone to mutation. I took it this was the kind of thing Alexis was thinking of. Of course, if I’m right to think this could have happened, there’s no reason species couldn’t be naturally selected, under certain circumstances, for being especially resistant to mutation, as well. So there’s no reason to think natural selection would, if “left to its own devices” so to speak, prefer one option to the other. -FrL- ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [August 19, 2006, 5:38am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/25 "2006-08-19T05:38:28Z")
> [@John Mace](#): > > It’s quite likely that bipedalism did, as a byproduct, spur further brain development since it feed up the hands for many other uses, but that came long after the adaptation to upright walking occured. I’m getting a little sidetracked. My original argument, which I think is the more interesting and profound hypothesis for discussion, is that when you say something encouraged the evolution of intelligence, that same exact stimulus for a different branch of mammals would not have given rise to humans. The evolution of intelligence is **not** the accumulation of genes which increase brain size. Partly, it is the accumulation of genes which allow the brain to get wired. Mostly, however, it is the accumulation of genes which increase the pace of the accumulation of genes which allow the brain to get wired. Genes speeding up evolution is my point. There does seem to be an accelerating curve of human accomplishment. We’ve been evolving for 10m years, yet it’s surprising how much has happened in the past 150,000. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 5:41am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/26 "2006-08-19T05:41:56Z")
> [@Alex\_Dubinsky](#): > > I’m getting a little sidetracked. My original argument, which I think is the more interesting and profound hypothesis for discussion, is that when you say something encouraged the evolution of intelligence, that same exact stimulus for a different branch of mammals would not have given rise to humans. The evolution of intelligence is **not** the accumulation of genes which increase brain size. Partly, it is the accumulation of genes which allow the brain to get wired. Mostly, however, it is the accumulation of genes which increase the pace of the accumulation of genes which allow the brain to get wired. > > Genes speeding up evolution is my point. > > There does seem to be an accelerating curve of human accomplishment. We’ve been evolving for 10m years, yet it’s surprising how much has happened in the past 150,000. But is there much, if any, evidence that _evolution by natural selection_ has had any effect on our species over that timespan? -FrL- ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 5:43am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/27 "2006-08-19T05:43:30Z")
> [@Alex\_Dubinsky](#): > > Mostly, however, it is the accumulation of genes which increase the pace of the accumulation of genes which allow the brain to get wired. Where are you getting the idea that this occurs or occured? Are you speculating? Are you arguing this is how it must have happened? Are you repeating something researchers have theorized already? Or what? -FrL- ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [August 19, 2006, 5:43am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/28 "2006-08-19T05:43:41Z")
> [@Frylock](#): > > I would have thought that species could be naturally selected, under certain circumstances, for their being especially prone to mutation. I took it this was the kind of thing Alexis was thinking of. > > Of course, if I’m right to think this could have happened, there’s no reason species couldn’t be naturally selected, under certain circumstances, for being especially resistant to mutation, as well. So there’s no reason to think natural selection would, if “left to its own devices” so to speak, prefer one option to the other. > > -FrL- Yup. What about extending your concept a bit to speeding/slowing mutations in just a single target organ or a target gene? ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 5:51am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/29 "2006-08-19T05:51:21Z")
> [@Alex\_Dubinsky](#): > > Yup. What about extending your concept a bit to speeding/slowing mutations in just a single target organ or a target gene? I don’t see how it makes any difference whether I say “among humans, a four chambered heart was selected for” or instead “humans were selected for having a four chambered heart.” In other words, sure, I guess you could say evolution “targets” particular organs or even genes in some sense, but only inasmuch as it selects those particular individuals (or species) which these organs/genes belong to. -FrL- ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [August 19, 2006, 5:57am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/30 "2006-08-19T05:57:27Z")
> [@Frylock](#): > > > [@](#): > > > > Originally Posted by Alex\_Dubinsky > > Mostly, however, it is the accumulation of genes which increase the pace of the accumulation of genes which allow the brain to get wired. > > Where are you getting the idea that this occurs or occured? Are you speculating? Are you arguing this is how it must have happened? Are you repeating something researchers have theorized already? Or what? I am arguing that this is how it must have happened. Is that alright by you? In regard do your last post, I mean that at the same time one gene/subsystem might have been stimulated to mutate more while another’s mutation has been suppressed. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [August 19, 2006, 6:02am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/31 "2006-08-19T06:02:11Z")
> [@Alex\_Dubinsky](#): > > I am arguing that this is how it must have happened. Is that alright by you? Sure, perfeclty fine by me… not sure why you would ask… So my next question is, why do you think it must have happened that way? You’re saying it must have been that humans were selected to have brains especially prone to mutation. Why? > [@](#): > > In regard do your last post, I mean that at the same time one gene/subsystem might have been stimulated to mutate more while another’s mutation has been suppressed. Hmm… I’m not sure if this is possible or not. I can’t see any reason why not. Wonder if there is a more knowledgeable person reading who can say something about it. -FrL- ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [August 19, 2006, 6:04am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/32 "2006-08-19T06:04:26Z")
> [@Alex\_Dubinsky](#): > > I’m getting a little sidetracked. My original argument, which I think is the more interesting and profound hypothesis for discussion, is that when you say something encouraged the evolution of intelligence, that same exact stimulus for a different branch of mammals would not have given rise to humans. The evolution of intelligence is **not** the accumulation of genes which increase brain size. Partly, it is the accumulation of genes which allow the brain to get wired. Mostly, however, it is the accumulation of genes which increase the pace of the accumulation of genes which allow the brain to get wired. > > Genes speeding up evolution is my point. > > There does seem to be an accelerating curve of human accomplishment. We’ve been evolving for 10m years, yet it’s surprising how much has happened in the past 150,000. We’ve been evolving for a lot longer than 10M years. This is GQ, and you really should get your facts straight before posting here. Frankly, it looks like you don’t know much about evolution and you might want to read up on the subject or simply ask questions here rather than posting random thoughts as if they were credible scientific information. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [August 19, 2006, 7:06am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/33 "2006-08-19T07:06:46Z")
> [@Alex\_Dubinsky](#): > > I’m trying out a compact writing style. Too bad it’s an excuse for you to tell yourself denial is a river in Egypt. There’s a pun in there, but you managed to butcher it. > [@](#): > > I very clearly say bipedalism began evolving in apes long ago, and further argue that its sophistication has mirrored the growth of intelligence. You made an argument earlier that bipedalism in humans was a result of the development of greater brain power. I pointed out that the fossil record leads us to precisely the opposite conclusion, as we can see in the fact that our ancestors developed bipedalism _before_ there is any evidence of our increased brain power in comparison to our relatives. > [@](#): > > I don’t understand why you assume bipedalism to be so computationally easy. You have to not only keep track of where dozens (hundreds?) of joints and muscles are, but you have to compute with exquisite precision where they will be. You do this not just by considering their velocities, but their momenta, kinetic energies, and frictions. Most challenging of all, you have to incorporate visual information and the 3D map of surroundings that it generates. And you must do all this repeatedly, all the time, every couple of dozen milliseconds. And you have yet to provide any argument to prove that it is particularly more difficult than any number of other types of locomotion. Walking on two legs seems much simpler than, for instance, brachiating. And yet we have much larger brains and higher intelligence than our tree-dwelling ancestors. > [@](#): > > Excalibur, I know you don’t like me. But you have a habit of letting it cloud your rationality. You can keep your irrelevant opinions of other posters in an appropriate forum. This is not the place to air your uninteresting grievances. > [@](#): > > Of course I’m not saying that because you disagree with me you are stubborn. But replies of “I don’t know what you’re saying and I’m refusing to try to understand it” only belie your intelligence. A poorly-written paragraph full of poorly-formed thoughts is a challenge to read. I don’t think clear communication would be served by my guessing at what I think you might want to say. > [@](#): > > Actually, that’s a very good point. I still believe opposable thumbs themselves evolved in the trees where bipedalism is N/A. However, opposable thumb precision, unlike what I had been leaning towards before, was probably more directly a biproduct of bipedalism and not of intelligence per se. You keep making arguments and presenting no evidence. It’s unclear why you think brachiation would require less dexterity with the hands than walking on two feet does. ---
**Author:** ![Excalibre](https://avatars.discourse-cdn.com/v4/letter/e/898d66/32.png) [@Excalibre](https://boards.straightdope.com/u/Excalibre)\ **Post date:** [August 19, 2006, 7:13am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/34 "2006-08-19T07:13:44Z")
> [@John Mace](#): > > We’ve been evolving for a lot longer than 10M years. > > This is GQ, and you really should get your facts straight before posting here. Frankly, it looks like you don’t know much about evolution and you might want to read up on the subject or simply ask questions here rather than posting random thoughts as if they were credible scientific information. I think this point deserves some particular emphasis. There’s a big difference between guesswork and empirical reasoning; keeping an argument firmly-grounded in evidence leads one to avoid making erroneous conclusions that seem logical at the time. Aristotle apparently wrote that women had fewer teeth than men. He was clearly making such an argument based upon his own guesswork - and he never thought to check his theory by, say, counting his wife’s teeth. He would have learned, if he had, that his theory was wrong. That’s why we encourage the use of citations here. Alex Dubinsky’s posts in this thread have revealed a profound misunderstanding of what “evolution” means; from the beginning, he has argued that evolution works towards a goal and indeed he imputed conscious decisionmaking to it. The notion of evolution as something teleological is a common mistake among the uneducated. (I’ve thought for a long time that Intelligent Design actually has a certain benefit: it inherently rejects this teleological conception of evolution, and I wonder if its dissemination is at least correcting some ignorance in regard to the subject that many people have.) At any rate, it might be a more productive discussion if Mr. Dubinsky would spend some time doing research - both learning the basics of evolutionary theory and finding evidence for the claims he wishes to make - if he wants to continue discussing the subject. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [August 19, 2006, 8:17am UTC](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411/35 "2006-08-19T08:17:41Z")
> [@Frylock](#): > > I would have thought that species could be naturally selected, under certain circumstances, for their being especially prone to mutation. I took it this was the kind of thing Alexis was thinking of. Being prone to mutation doesn’t necessarily help in terms of the rate of evolution. It largely just increases the odds of beneficial mutations appearing (as well as increasing the odds of detrimental ones appearing, and of selectively neutral ones appearing…). See [this old thread](http://boards.straightdope.com/sdmb/showthread.php?t=123396) wherein we discussed the effects on evolution of so-called “heat shock” genes, which effectively serve to do pretty much just what you suggest (make a population “especially prone to mutation”), under times of extreme stress. Now, it can perhaps be said that life has [evolved to be more evolvable](http://www4.tpgi.com.au/users/jes999/gencog.htm). But that evolvablity is a function of how organisms (and more specifically, their genomes) are put together (and how they are put together is a function, of course, of how they evolved), not a function of natural selection itself being altered to operate differently or more efficiently; the result is that the _rate_ of evolution has not necessarily increased because of the evolution of genetic systems as mentioned in the linked paper, but the _efficiency_ has. Instead of a wide range of possible variation, variation can be reduced to certain known-to-be-viable ranges, which reduces the amount of trial-and-error that has to occur before a beneficial mutation is found. In essence, then, variation can either be restricted or unhindered, and both represent viable evolutionary strategies in different circumstances. But the selection that occurs on that variation still operates in the same manner, regardless. [Previous page](https://boards.straightdope.com/t/the-evolutionary-utility-of-the-opposable-thumb/368411.md?page=1)